LEVEL FLOTATION 

Flotation regulations for outboard powered greater than 2 HP recreational boats. 33 CFR 183.201-235

Applies to:

Mono-hull Boats (not catamarans, trimarans, or pontoon boats): Mono-hull means that if you can draw a continuous line around the hull at the waterline when the boat is at rest it's a mono-hull. If it makes two or more footprints in the water it's a multi-hull.

Greater than 2 Horsepower:

Less than 20 feet (measured on the center line, including rub rails):

This category includes most outboard motor boats.

Standards for Electric Propulsion boats, for Flotation, Safe Loading and Maximum Horsepower Ratings.

The U.S. Coast Guard has published a policy letter regarding standards for Flotation, Safe Loading and Maximum Horsepower ratings on boats with electric propulsion.Essentially the policy letter says that manufacturers of electric propulsion recreational boats should comply with the same standards for Safe Loading, Flotation, and Safe horsepower as gasoline powered recreational boats,  and refers to ABYC Standard E-13 Lithium Batteries and E-30 Electric Propulsion Systems for Boats with Electric Propulsion. The policy letter can be seen at the Coast Guard's website at https://safeafloat.com/wp-content/uploads/2022/08/BSX-23-Electric-Propulsion-Policy-FINAL.pdf

Electric boats must follow the same requirements for flotation and flotation foam as that for gas powered boats. For electric boats use the published weight of the outboard, or inboard motor.

Requirements:

The boat has to float when swamped, (that is; full of water), in an upright attitude. See the diagram in each test for the specific requirements.

So how do I know how much flotation to put in the boat?

The amount of flotation is based on three factors.

1. The boat weight: that is the weight of the hull, the deck, the seats, etc. Everything not in the next two categories.

2. The weight of the engines, batteries, full portable fuel tank, or full permanetly installed fuel tank, and controls. See the table.

3. The weight of the persons. This comes from the persons weight on the capacity label.

Go to page on how to calculate amount of flotation.

What do I use for flotation?

Most people use polyurethane foam. Some use polystyrene foam. If you use polystyrene foam you must install it in a way that it cannot be attacked by gasoline, oils or bilge cleaners. See 33 CFR 183.112-114 on flotation materials.  Others use air chambers. Air chambers that are integral with the hull are not allowed. They must be separate from the hull. Also, you have to pass the test with the two largest chambers punctured. Foam is a good solution, but some don't want foam in their classic wooden boats. In that case they can use balsa, or build air chambers into the boat. There are other ways to provide flotation, however, some ideas are not that good. The two main reasons boats fail is not enough foam, and not enough foam to support the engines.

Excellent article in the USCG Boating Safety Circular #98 Spring 2022 concerning quality Control for floatation Foam.

Some people will tell you Styrofoam flotation is banned by the Coast Guard.

Not True:  Styrofoam may be used as flotation.

33 CFR Subpart F - 183.101 -183.335 Flotation

§183.112   Flotation material and air chambers.
(a) Flotation materials must meet the requirements in §183.114 as listed in Table 183.114 when used in the: (1) Engine room bilge, (2) engine room, or (3) bilge, unless located in a sealed compartment.

Any means can be used to achieve the flotation requirements such as foam, air chambers, balsa, and other materials.  The Coast Guard requirement says that if you use flotation materials and if the flotational material is exposed to gasoline, oils or other chemicals that would degrade it, it must be resistant to these substances.  The most common flotation material is foam.  Some are resistant to degradation.  Polyurethane foam is.  Styrofoam is not because it is made of polystyrene. Be aware that not all polystyrene foams are "Styrofoam". Styrofoam is a trademarked name. There are other insulation type foams made of polystyrene that can be used as flotation foam. However, you can use Styrofoam or any polystyrene foam anywhere it isn’t exposed to these substances, or anywhere if the foam is encased. Foam isn’t even required. It just happens to be the easiest and most convenient solution.

I have heard others say they are planning on using Coast Guard Approved Flotation Foam" 

Not True: 33 CFR Subpart F - 183.101 -183.335 Flotation See 183.114.  The USCG does not approve or certify flotation foam. Approval applies to certain items you must carry on board a boat. This includes things such as Fire Extinguishers, Personal Flotation Devices, and visual distress signals. Also some courses and schools for professional mariners are Coast Guard Approved. Flotation foam is not. Anyone telling you they are selling Coast Guard approved flotation foam is violating the law and lying to you. If they say it meets the requirement of 33 CFR 183.114 then that means they, the foam manufacturer,  have tested it for resistance to gasoline, oils, bilge cleaners, etc. and it can be used in the bilge or areas where it is exposed to these things. But that is not Coast Guard Approval. Approval means that the Coast Guard has not only looked at the item and inspected it, but also tested it to see that it meets all of the regulations that apply. The Coast Guard does not do that for flotation foam.

However, there are some foams used as insulation on ships, that are Coast Guard Approved for fire resistance, meaning the Coast Guard has had them tested for fire resistance. Conceivably they could be used for flotation but that is not their intended use.

Coast Guard Certification and Approval:

US Coast Guard Approval:

How do I know it works?.

Test it!

The best way to find out if your boat passes is to test it. You can do the test yourself, or have a laboratory do it.  However, as of June 2014 the USCG Voluntary testing program has ended. The Coast Guard will no longer test your boat for free.  You will have to pay the laboratory to test the boat for you.  Call the Coast Guard at or 202-372-1077 to find out about the test program.  The Coast Guard still purchases and test boats they suspect are not in compliance and cannot pass the flotation requirements. If this happens you will have to do a recall on all boats of that year and model, so it is better to test it before you start selling them. 

Here's how it's done.

You need to know the following:

The maximum weight capacity (the safe load ) your boat will carry.

How much weight in people it will carry.

The engine weight. See the table at https://newboatbuilders.com/pages/table4.html

There are some things you also need to know before you do the test. What kind of weights will you use for the test? The test lab uses iron ingots. You can use anything that does not absorb water, which leaves out concrete or concrete blocks. You also need to weigh each of the weights with a calibrated industrial scale. These can be rented from companies that rent equipment for labratories.

You need to determine if the test weights will be submerged or dry. In the capacity tests the weights are dry, but in the flotation test they will most likely be submerged. Submerged they weigh less than they do dry. This is not difficult to calculate. The USCG, and ABYC publish tables of factors (determined from the specific gravity of the weight) for different materials. For iron the factor is 0.86. That is you need to add weight for iron, because under water it weighs less. For example if the amount of weight needed is 200 lb., you need to add 33 lbs to compensate for it's reduced weight underwater. (200/0.86 = 232.5 dry weight)

The table for the factors is at https://newboatbuilders.com/pages/factors.html

If the boat has a permanently installed fuel tank, you need to test it as if the tank were full. On some boats the tank may be high enough to be dry when the boat is full of water. But on most boats it is submerged. .

The USCG recommends you do not test the boat with gasoline in the tank. This could result in environmental issues, and safety issues. Test the boat with the tank empty, preferably before the tank has ever been filled. You could put water in the tank and compensate for the difference in weight between water and gasoline. (Gasoline is about 6 lb per gal, fresh water is about 8 lb per gal). But then you can have difficulty getting all of the water out of the tank. So it is best to test it empty.

If it is dry (out of the water) then simply use the same amount of weight as fuel. For example a 40 gal tank x 6 lb/gal = 240 lb. you need to place the weights so they have the same center of gravity that the tank would have if full. Weight on the top and some on each side would work.

If the tank is submerged you need to calculate the weight as if full, and then determine what the weights would weigh submerged. For instance if it is a 40 gallon tank, and you are using iron weights then:

240lb/0.86 = 279 lbs. or you can use the formula the USCG uses, 40 gals times 7.1523 = 286 lbs. I recommend you use the Coast Guard formula.

Then measure the following on your boat:(Click image for full size) Cockpit area. 40% reference area. Passenger area 70% reference areas. Two foot reference areas fore and aft. There are three tests to do.

TEST 1. The first is the level flotation test after an 18 hour soak.

Put your boat in the water. Put ½ the persons weight in the boat (assuming the maximum persons weight is less than 550 pounds. If over 550 pounds, add .125 times persons weight minus 550) in the 40% reference area. The Center of Gravity of all the weights needs to be in the 40% reference area. That doesn't mean all the weights have to be in the 40% area, just the Center of Gravity of all the weights. Pull the plug! Let the boat fill up with water. Leave it that way for 18 hours.

When you come back it should float like this: (Click image for full size) One end out of the water. The other end 6 inches or less under water (or out of the water too) measured at the 2 foot reference area. No more than a 10 degree heel angle. (You can buy a device at a hardware store that measures this).

TEST 2. The second test is the stability test. You need to do this one twice, once on each side of the boat.

Place ½ the weight for persons on one side of the boat. The center of gravity of these weights has to be in the 70% reference area on that side of the boat. You have a lot of lee way here. You can move the weights from front to back, or back to front to get the boat to pass as long as the Center of Gravity is in the 70% area, and 30% of the total passenger weight is in the 70% area.

Take the other ½ of the passenger weight out of the boat.

Leave the engine, batteries, fuel and control weights where they are.

WARNING! Make sure you have some ropes or straps attached to the boat to keep it from rolling over. If you don't have enough flotation to keep it upright, that's what it will do. Then the weights will fall out and go to the bottom of the pool or lake.

When it settles down it should float like this. (Click image for full size) One end out of the water. The other end 12 inches or less under water (or out of the water too) measured at the 2 foot reference area. No more than a 30 degree heel angle. Experience has shown that if it goes 30 degrees it will probably roll all the way over.

REPEAT THIS TEST ON THE OTHER SIDE.

TEST 3. The final test is without the passenger weights.

Take all of the passenger weight out of the boat. Let the boat settle. It should float like this: (Click image for full size) One end out of the water. The other end 6 inches or less under water (or out of the water too) measured at the 2 foot reference area. No more than a 10 degree heel angle.

That's It! If you pass all these tests you have done everything the regulations require.

The most common reasons for failing the flotation Test;

Not enough flotation: (But you can also fail if you have too much flotation.)

Flotation in the wrong locations in the boat.

Incorrect flotation foam density:  The calculations use 2lb density.  That is, one cubic foot of foam weighs 2 lb. If you use heavier (or lighter) you will fail unless you actually use a denser or lighter foam and use it's density in the calculations:

Improper kind of foam in the bilge: Flotation foam that is resistant to exposure to gas, oils, bilge cleaners, or anything that can dissolve or damage the foam, is usually polyurethane. But some manufacturers use polystyrene foams, the most common of which is Styrofoam (a trademarked name).  Stryofoam, and all polystyrene foams, will be dissolved by gas, oils, bilge cleaners, etc. They must not be used in the bilge or anywhere they can be exposed to those solvents unless encapsulated so they can't be contacted.